conftypes: Use special SYSTEM_PROXY object instead of 0.

qutebrowser/config/conftypes.py

@@ -31,6 +31,9 @@ from PyQt5.QtNetwork import QNetworkProxy
 import qutebrowser.commands.utils as cmdutils
 
 
+SYSTEM_PROXY = object()  # Return value for Proxy type
+
+
 class ValidationError(ValueError):
 
     """Exception raised when a value for a config type was invalid.
@@ -997,7 +1000,7 @@ class Proxy(BaseType):
         if not value:
             return None
         elif value == 'system':
-            return None
+            return SYSTEM_PROXY
         elif value == 'none':
             return QNetworkProxy(QNetworkProxy.NoProxy)
         url = QUrl(value)

qutebrowser/network/proxy.py

@@ -20,6 +20,7 @@
 """Handling of proxies."""
 
 import qutebrowser.config.config as config
+from qutebrowser.config.conftypes import SYSTEM_PROXY
 
 from PyQt5.QtNetwork import QNetworkProxyFactory
 
@@ -43,9 +44,7 @@ class ProxyFactory(QNetworkProxyFactory):
             A list of QNetworkProxy objects in order of preference.
         """
         proxy = config.get('network', 'proxy')
-        if proxy is None:
-            # config.get returns a QNetworkProxy for all cases, except when we
-            # should use the system proxy -- then it returns None.
+        if proxy is SYSTEM_PROXY:
             return QNetworkProxyFactory.systemProxyForQuery(query)
         else:
             return [proxy]